Research

Segregation-induced ordered superstructures

  • By Burcu Ozden
  • 21 March 2018

Michael Widom and his colleagues showed what happens at the grain boundaries of one particular alloy of the metals nickel and bismuth that makes it brittle in their paper published in Science. Using advanced electron microscopes, Widom’s collaborators at Lehigh University scrutinized these microscopic grain boundaries at an atomic level. In a "very heroic experimental program" they discovered that when grains met, the bismuth and nickel atoms realigned into lattices to form layered superstructures at the grain boundaries. These superstructures had previously been thought to exist only rarely in some alloys. Finding it at many different boundaries led the team to conclude that these superstructures are probably much more common than many people had thought. 

Chiral nanocluster with open shell electronic structure and helical face-centered cubic framework

  • By Leena Aggarwal
  • 2 March 2018

Owing to high surface to volume ratios and chemical potential, nanoparticles possess unique optical, electrical, and thermal properties, which constitute the basis of novel applications in sensing, catalysis, nanoelectronics, bio-tagging etc. Despite the great advances in the synthesis, the total structure determination of nanoclusters still remains to be a major challenge. Recently Hyung J. Kim and their colleagues have reported the synthesis and crystal structure of a nanocluster composed of 23 silver atoms capped by 8 phosphine and 18 phenylethanethiolate ligands in the journal of Nature Communications.

Engineering of spin canting across core/shell Fe3O4/MnxFe3−xO4 nanoparticle

  • By Leena Aggarwal
  • 27 February 2018

In the recently published paper in Scientific Reports, Sara A. Majetich and their colleagues have demonstrated the engineering of spin canting across a Magnetic nanoparticles (MNP) via the Dzyaloshinskii-Moriya interaction (DMI). In this paper, they have shown that strong DMI can lead to magnetic frustration within the shell and cause canting of the net particle moment. These results have illuminated how core/shell nanoparticle systems can be engineered for spin canting across the whole of the particle, rather than solely at the surface.

 

Building Smarter Windows

  • By Burcu Ozden
  • 21 February 2018

Paul Leu and his student Sajad Haghanifar, a PhD candidate, developed a new type of glass 1,000 times thinner than a human hair which could potentially used as solar panels for smart windows.

While the solar energy industry is expanding — at an average annual rate of 68 percent from 2006 to 2016, according to the Solar Energy Industries Association — solar panels and solar cells still have an efficiency issue.

Paul Leu said, " Any light that is not being absorbed by your solar cell is decreasing the efficiency of your solar panel," and added “Anything you can do to increase your efficiency is good.”

Leu said that the new glass they developed has advantagous of scattering light energy at different angles, giving the light that does bounce off a better chance to be trapped and converted into useable energy

He added, “With these nanostructures, you can get the reflection rate close to zero.” 

Electron Transfer without Overcoming a Barrier

  • By Burcu Ozden
  • 14 February 2018

In the recently accepted paper in Physical Review Letter, Hrvoje Petek and his colleagues investigate the coherent electron transfer from an interface state that forms upon chemisorption of Ag nanoclusters onto graphite to a σ symmetry interlayer band of graphite. Interfacial charge transfer is a fundamental process in heterogeneous and plasmonically enhanced catalysis.

Susan Fullerton and colleagues are one of five winners of international circular materials challenge

  • By Burcu Ozden
  • 24 January 2018

Each year more than eight million tons of plastics pollute the ocean, forming mammoth, so-called “garbage patches” via strong currents. Even with new collection methods, only 0.5 percent out of that volume is currently removed from the seas. One solution to this growing crisis is to prevent plastic from becoming waste, to begin with – and Susan Fullerton and colleagues are one of five international teams awarded for their novel solutions to this problem. The group was one of two winners in Category 1: “Make unrecyclable packaging recyclable,” and proposes using nano-engineering to create a recyclable material that can replace complex multi-layered packaging – mimicking the way nature uses just a few molecular building blocks to create a huge variety of materials.

Understanding the Link Between Photonic and Electronic Performance of 2D Semiconducting Layers

  • By Burcu Ozden
  • 20 December 2017

Susan Fullerton and her colleagues wrote a scientific report on deconvoluting the photonic and electronic response of two-dimensional (2D) materials for the case of molybdenum disulfide (MoS2). What are the main criteria which provide evidence that the material is “high quality”? Are the photonic properties or electronic performance? Susan Fullerton and her colleagues have studied the MoS2 materials and their devices to answer this question and to find the correlation between electronic and optical properties in 2D materials. In their study, they used Raman, photoluminescence (PL), time-resolved photoluminescence (TRPL), high-resolution scanning transmission electron microscopy (HR-STEM), X-ray photoelectron spectroscopy (XPS), field effect transistors (FET) fabrication electrolyte gate application methods to characterize MoS2.

Webinar on Multidisciplinary University Research Initiative (MURI)

  • By Burcu Ozden
  • 13 December 2017

Last month University of Pittsburgh host a webinar titled as “Guide to Research Roadmap: Multidisciplinary University Research Initiative (MURI) in collaboration with Mcallister and Quin consulting firm. As Pittsburgh Quantum Institute, we attended this event to be able to share the information on this webinar with our members. The purposes of the webinar were to explain the crucial steps needed to proactively plan for the MURI program and using the McAllister & Quinn (M&Q) MURI Research Roadmap (available to PQI members with e-mail request). In this article, we would like first to discuss briefly what the M&Q MURI Research Roadmap is and how our members can reach this information and then summarize the topics discussed in this webinar.

Discovery of a Mechanism for Dislocation Nucleation and Migration Driven by Surface Segregation

  • By Burcu Ozden
  • 6 December 2017

Judith C. Yang and her colleagues answered the question of how dislocations nucleate and migrate at heterointerfaces in dissimilar-material systems on their recently published article on Nature Materials. n this study, Judith Yang and her colleagues showed that atomic segregation acts as a source for generating dislocations for the first time. They have used Cu–Au alloy system for studying surface segregation. Real-time transmission electron microscopy (TEM) was used to both spatially and temporally resolve the transition of the coherent, dislocation free interface between a Cu3Au-segregated surface and a Cu(Au) crystal substrate into a semi-coherent structure through the nucleation and subsequent migration of misfit accommodating dislocations. They combined their experimental study with the teory by using density functional theory (DFT) and molecular dynamics (MD) simulations. They discovered a mechanism for dislocation nucleation and migration driven by surface segregation of solute atoms in a solid solution. Their results show that the surface-segregation-induced composition variations act as the source of strain/stress that drives the nucleation and migration of misfit dislocations, and demonstrate how the surface segregation phenomenon of an alloy constituent can be employed for developing atomistic insight into understanding the formation processes of misfit-accommodating dislocations.

Where are hot carriers created in plasmonically enhanced semiconductor substrates?

  • By Burcu Ozden
  • 5 December 2017

PQI members Hrvoje Petek, Jin Zhao and their colleagues investigated a less known fact about the microscopic details of how the combined optical, electronic and chemical properties of metal/semiconductor interfaces define the coupling of light into the electronic reagents on their recent paper published in Nature Photonics. In this study, they investigated the coherence and hot electron dynamics in a prototypical Ag nanocluster/TiO2 heterojunction via ultrafast two-photon photoemission (2PP) spectroscopy, scanning tunneling microscopy (STM) and density functional theory (DFT).  The silver nanoclustors used in this study were grown via e-beam evaporation of Ag on top of TiO2 surface.They have shown that the plasmon excitation, dephasing and hot electron processes that are related to plasmonically enhanced photocatalysis involve complex physical and chemical interactions, with strong interfacial character involving the chemical and plasmonic coupling of Ag nanoclusters and the TiO2 substrate that cannot be predicted by the properties of the component materials, but rather require an understanding of their interactions. They found that the dephasing of the perpendicular and parallel plasmons by the dielectric screening response of the TiO2 substrate generates hot electrons with anisotropic and non-thermal distributions.

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